We also derive the mass loss rate based on measurements of the student dust counter on the New Horizons mission [1]}. The number of particles between 0.5 and 5 microns hitting the student dust counter in the KB at 45 au, moving at \(v_{\rm NH} \sim 14\)  km/s, is estimated to be \(F_d=1.5 \times 10^{-4}\)  m\(^{-2}\)  s\(^{-1}\)  [2]}. The total mass of grains is then given by \(M_d[0.5-5{\mu }m]=(F_d / v_{\rm NH}) \, m^* S_{\rm KB} (2 H)\) , where \(m^*\)  is the mean mass of a particle in the 0.5-5 micron size range given a particle size distribution slope in -2.5 as it is in the PR-drag (rather than collisional) regime [3]}, [4]}. To get the mass loss rate of grains between 0.5 and 5 microns, we divide by the PR-drag timescale \(t_{\rm PR}=400 \beta ^{-1} (R_{\rm KB})^2\)  [5]}, where we take the ratio between the radiation pressure force to that of stellar gravity \(\beta =0.2\)  based on the mean size of a grain of mass \(m^*\)  [4]}. However, to get the mass loss rate of the cascade (and not just that of the grains captured by the student dust counter), we need to multiply by the number of logarithmic bins up to the size at which collisions dominate over PR-drag [3]}, i.e., up to \(s_{\rm pr}=100\)  microns [4]}. We obtain \(\dot{M}_{\rm COtot}=9 \times 10^{-10}\)  M\(_\oplus \) /Myr, i.e. a gas production rate very close to that found with the previous method.
